1. Field of the Invention
This invention generally relates to a home automation system and, more particularly, to an interface between a host computer and a network, to a watchdog timer, to a method of polling nodes, to a software message scheme, to a common method of controlling sub-systems in the home automation system, and to a button keypad assembly.
Additionally, this invention relates to a temperature sensor for accurately measuring ambient temperature. More specifically, it relates to an apparatus for providing a temperature-indicating signal to a home automation system which maintains a desired temperature in a closed environment.
2. Description of the Prior Art
FIG. 1 illustrates a network configuration of a prior art home automation system. The network comprises a host computer 10 set up in a daisy-chain configuration with a plurality of nodes 12, 14, and 16. The network has synchronous communication between the host computer 10 and the nodes whereby each message transmitted from the host computer 10 passes through each node. With this system, each message passes through each node until the message reaches the node addressed by the transmitted message. This node receives and processes the message and then transmits the message to the next node. Each node has a transceiver for receiving the message from a previous node and for transmitting the message to the next node. The host computer 10 receives the circulated message from the last node in the loop and checks the message for errors.
The message is comprised of a command byte, a node byte, and one data byte. The command byte indicates whether the message is just a command or if it also has a data byte along with the command. The node byte identifies the node to which the message is directed and the data byte contains the actual data. Therefore, for instance, to update the display of an LCD display at some node on the network, each character in the display had to be sent to the node with a different message. As another example, in order to dim the lights, messages were continuously transmitted to the node until the accepted level was reached.
Each byte is individually transmitted onto the daisy-chain network where it is circulated around the network to each node. The host computer 10 waits until a byte has been completely circulated around the loop and then checks the byte for errors. The node byte can address up to 80 different nodes and contains a node ID data segment and a connection data segment.
As should be apparent from the above description, the prior art home automation system uses a short data link resulting in relatively slow communication between the host computer 10 and the nodes. Also, a failure of a node in the loop disables the entire network by producing a discontinuity.
Additionally, in the prior art home automation system, with reference to FIG. 2, the host computer 10 received operating power from a central PC power supply 19, which also supplied power to the various nodes 12, 14, 16, and 17 in the network. With this system, when the supply of power to the host computer 10 is interrupted, the various nodes in the network would also be disconnected from power. Thus, a single power failure could disable the entire system, including the security system. In addition to the problems in reliability, the prior art power system could only accommodate a limited number of components. Thus, the prior art home automation system was limited in its ability to expand to accommodate more nodes.
Furthermore, previous prior art home automation systems are typically a collection of sub-systems produced by different manufacturers which are designed to work as stand alone systems in the home. These prior art home automation systems combine the third party sub-systems, such as lighting control sub-systems, audio/video control sub-systems, and security sub-systems, and provide limited communication to a central computer with automation software.
With such a prior art home automation system, a user needs to learn how to operate each one of the sub-systems. Additionally, if communication is necessary between the user and the sub-system, the user must learn how to use the interface to the central computer or must call a service representative to make any desired changes to the system. Thus, the user must learn a separate manner of operating and communicating with each sub-system in the home automation system, which is typically between four and six sub-systems.
For instance, a prior art home automation system may use an existing home security system with its own unique keypad and set of keystrokes and link it to a central controller. A prior art home automation system may also connect the central controller to an existing lighting system, with its own unique keypad and set of keystrokes to control the lighting. Other sub-systems, with their own unique methods and devices for communicating with a user, may also be connected to the central controller. For a user to control the security system, to control the lights, and to control the other sub-systems, the user must learn how to interface with the security sub-system, the lighting control sub-system, as well as the other sub-systems.
A problem exists with this system in that it becomes rather difficult and complicated for a user to properly control each system. Because each sub-system has its own unique device and method of interfacing with the user, it becomes even more difficult and burdensome for a user to operate the prior art home automation system.
As a result, users of home automation systems typically do not operate the home automation system to its full capacity. Instead, a technician will set up the home with several global scenarios over which the home owner will have limited control. If the user desires a change in the system or wishes to take advantage of the system's capability, a technician is typically called to do the interfacing with the system.
The prior art home automation systems may be used to automatically control a variety of activities such as turning lights and appliances on and off. Additionally, such systems may be used to regulate the ambient climate in a closed environment such as a home or office. Climate control may include the maintenance of a desired ambient temperature or humidity level.
The most common method of maintaining a desired ambient temperature in a closed environment is to provide a temperature sensor together with a thermostat. However, many conventional home automation systems utilize solid state components in such arrangements which are continuously active. This results in the generation of heat which introduces error into the temperature sensing circuit. While it may be attempted to shield the sensing component from the remainder of the circuit, the heat generated from active components is often not sufficiently eliminated.
Alternatively, the sensing component may be separated from the remainder of the sensing circuit in order to reduce the error introduced by the other components. It may also be separated in order to place it in an optimum location in a particular environment, for example away from direct sunlight or from heating or cooling ducts. However, if the sensing component is separated from the remainder of the circuit by a relatively large distance, error is introduced in the reading from transmission noise and the like. This problem is particularly pronounced where a voltage signal is used to indicate the ambient temperature.
Accordingly, there is a need to provide a temperature sensing circuit capable of obtaining stable, accurate measurement of the ambient temperature in various closed environments. There is a particular need to provide a sensing circuit which is capable of providing accurate temperature measurements to a temperature control device separated by a relatively long distance and which does generates a relatively small amount of heat.
The prior art home automation system has several diagnostic features incorporated in both the hardware and software in order to overcome problems associated with failure of certain parts of the system. The basic approach of these features is to detect and indicate a failure in an aspect of the system. However, there remains a risk that the host computer 10 itself will fail, thereby eliminating the means by which the operator is alerted to a problem with the system. Hence there is a need to monitor the system and provide an indication that the host computer 10 no longer is operating.
The prior art home automation systems also used button interfaces that were prone to several problems. One problem was that the interfaces were relatively complex requiring strict tolerances between parts. It was therefore prone to improperly fitting parts. Another problem was that covers for the interfaces were not securely fastened to a backplate so that the cover would fall off rather easily. Thus, it was a problem in the prior art to provide an economical and securely fastened interface.